The invention relates to a method for measuring the completeness of a book block intended for adhesive binding by measuring the thickness of the book block passing on a conveyor through processing stations of an adhesive binding machine and comparing a measured actual measured value with a specific control value. The invention additionally relates to an arrangement for carrying out such a method.
For adhesive binding of printed sheets to form a book block (as used herein, the term "book block" includes a book block, per se, and a book, which is a book block with a cover), the individual printed sheets are deposited by sheet feeders of a gathering machine in a channel, in the correct sequence, one above the other to form loose blocks. In a transfer channel, these blocks are subsequently placed to stand on the folded edges of the printed sheets and are transferred to clamping devices of a conveyor that passes through the processing stations of an adhesive binding machine.
The mounted blocks with their folded edges project several millimeters over the clamping devices, so that they can be processed along this strip, which is referred to as an overhang.
At the various successively following stations of the adhesive binding machine, the book blocks are cut, notched, cleaned and glued together. Afterwards, they are generally provided with a slip fold or cover and are subjected to a drying or cooling to accelerate the hardening process, depending on whether hot-melt or cold-setting adhesive is used.
The completeness and correctness of the gathered printed sheets is checked in the gathering machine, in particular in the feeders, so that blocks with missing or excess printed sheets can be removed and/or replaced.
Based on experience, the control devices provided on the feeders are not capable of ensuring that a book block is complete, so that blocks formed from gathered printed sheets can reach the adhesive binding machine in error and are there processed as final products.